If it ain't cracked, don't worry about it. Does it say Dunlop on it?
Seasnarf gave me this link about LED wiring;
http://www.pilom.com/BicycleElectron...moCircuits.htm
Does it flicker faster when you go faster? That might be a magnet problem in the hub. I've thought about wiring these things in paralel with a couple of rechargable 1.5v batteries, partly to smooth out the pulsing and partially to have some light when I'm stopped and looking through the neighbor's trash or trying to identify a fallen tree. Don't know if it's a good idea. I need to look at those diagrams that seasnarf sent me a little more closely.
I still love that bike, Sean.